Field
Embodiments of the disclosure relate generally to the field of taped interlayer flow cells and more particularly to a method and structure for producing a taped interlayer flow cell with precision tape geometry and cell assembly including masking of the tape layer and conductive trace formation.
Background
Microfluidic devices, often referred to as flow cells, provide very precise means to carry out complicated biochemical reactions to acquire important chemical and biological information. Among other advantages, microfluidic systems reduce the required number of samples and quantities of reagents employed, shorten the response time of reactions, and decrease the amount of biohazard waste for disposal. First developed in the 1990s, initial microfluidic devices were fabricated in silicon and glass using photolithography and etching techniques adapted from the microelectronics industry. Many current microfluidic devices made using this method of fabrication are constructed from plastic, silicone or other polymeric materials, e.g. polydimethylsiloxane (PDMS). Such devices are generally expensive, inflexible, and difficult to construct.
Use of a tape interlayer to form the necessary microfluidic channels between two substrates was developed to reduce cost and complexity of fabrication. Typically a double-sided tape is used between two transparent substrates, which consists of a carrier material with an adhesive layer on the top and bottom and a removable liner covering the adhesive layers. Preferred double-sided tapes for all the embodiments described herein include double-sided silicone tape 3M 96042 or double-sided acrylic/silicone tape 3M 9731, but the choice of tape is dependent on the materials being used.
Microchannels are created by cutting out parts of the double-sided tape and covering it with a sheet of material—glass is preferable for the base, plastics can alternatively be used as the top or bottom cover. Microchannels can be created in plastics or other materials by embossing, etching, or any structuring method. Any number of microfluidic device components can be included on the tape. These might include, for example, microchannels, microvalves or other pneumatic elements, diffusion chambers, manifolds, holes that connect one layer to another (vias), inlet and outlet ports, and other microfluidic device components.
Conventional flow cell fabrication via molding, etching, and bonding is more expensive (both in required tooling and processing) and has longer lead time. In many cases, bonding methods to enclose the flow cell require high temperatures which prevent the use of many surface coatings and the encapsulation fluids or live cultures.
For prior art involving tape, no prior art fabrication methods provide capability for high precision formation of the flow channels. Additionally, imperfections in the tape as adhered to the substrates is aesthetically displeasing. In applications where the tape bonding to the substrates does not provide sufficient sealing no prior art technique is available to economically provide such sealing. Further, in many cases where electrical contact with the flow channels is needed, external leads must be employed. Finally, the prior art fabrication methods with tape cannot be accomplished on wafer level processing due to issues dicing the components on a wafer containing a tape layer.
It is therefore desirable to provide an apparatus and method to obtain high precision in flow channel shaping, provide visual masking to hide imperfections in the tape, provide additional room temperature bonding of substrate edges to obtain better channel dimensional properties or a fast customization of the flow cell. Additionally it is desirable to provide integral electrical leads to the flow cell. Further it is desirable to provide on wafer level processing for dicing the components on a wafer containing a tape layer.